AC Motor Measurement

[manyanez333]

hello everyone. My name is Manuel and I work in a company in Chile, in particular in the predictive maintenance field. I have some experience in LabView and for that reason I´m developing a system to measure voltage and current in industrial AC motor. In order to this I would like to know if NI has some module (in any kind of physical format, that means, cDAQ, PXI, cRIO, etc) to measure voltage over 550 V and current over 120 A. The other day I saw and instrument from other company which is used to detect failure in this kind of motors, and the main part was a NI module, but I couldn't see the model. I would appreciate if you can help me to find a module that satisfy this constraints.

Thank you

[chaka1234]

Hola Manuel, ¿Cómo estás?,

Al parecer lo que viste puede ser un DMM. Por ejemplo, el PXI-4071 puede medir hasta 1000V: http://sine.ni.com/nips/cds/view/p/lang/en/nid/14857.

Saludos,

Carmen Chan | Applications Engineering | National Instruments| 

[manyanez333]

Carmen. Thanks you fast reply. I check de DMM, but wasn't this, because the device that I saw has at least 3 Analog Input to measure voltage, and the DMM has only 2. Beside it was not a PXI card. If you know another kind of module to measure high voltage and current please let me know. Thanks again.

Take care

[johnsold]

Typically the way such measurements are made is via the use of potential transfomers and current transformers or voltage and current transducers. This keeps the high power circuits away from the daq acquisition and computer equipment. Consider that even something like the DMM module is not designed to handle the kinds of transients which can occur in a 100 kW motor environment. What happens to your equipment if the motor shaft siezes up or lightning strikes near the incoming feeder?

Lynn

[Buechsenschuetz]

I have no experience with measuring high AC voltages but rather with measuring AC current. As mentioned by others, usually current transducers are used which usually have output voltages of 1, 5 or 10V for full range. Even many clamp-on amp meters have an analog output.

When measuring AC voltages it should be no problem to use a transformer for galvanic isolation. In any case, for such high voltages there should be a sensor or at least a "front end" of the DAQ system which is complety isolated. I once designed a system for measuring up to 500VDC and we used a completely isolated ADC front-end, with isolated DC-DC converter supply and isolated data lines.